An ultra-compressible piezoresistive strain and pressure sensor based on RGO-CNT-Melamine foam composite for biomedical sensing

Many heitherto reported compressive piezoresistive foam sensors suffer from variable sensitivity over large compression range, limiting the applicability of the sensor for a narrow range of motion. This is because the area of contact between conductive foam struts is very small and varies linearly over only a small compression range. We resolved this problem by fabricating an ultracompressive foam sensor with large area conductive flakes using facile technique of soak-drying Melamine foam with the conducting aqueous RGO-CNT ink. Sensor exhibited a constant gauge factor (GF) 1.6 over a large and highly linear compression range (similar to 2% to 60 %) and detected both small and large body movements with superior detectability. Besides that all vital features of a tiny signal such as pulse waveform were delineated due to the excellent low pressure (<5 kPa) sensitivity 0.22 kPa(-1) and the small relaxation time of 19 ms. The sensor showed a stable and repeatable performance over 11000 cycles. Its operation is also tested over a wide range of ambient temperature (-7 degrees C to 140 degrees C) and humidity (25%-82%, RH) and even under water with no major deterioration in performance. (C) 2021 Published by Elsevier B.V.

Automated summary

Researchers have successfully developed an ultracompressive foam sensor with large area conductive flakes to address the issue of variable sensitivity in previously reported compressive piezoresistive foam sensors. The new sensor exhibits stable performance over a wide compression range, providing constant gauge factor and superior detectability for both small and large body movements. Additionally, the sensor demonstrates excellent sensitivity, short relaxation time, and stable operation under various environmental conditions, including underwater.